Your question is very general, so without specifics, here's what I would tell you. Choose a character that you relate to. If you value justice, choose Atticus. If you value bravery, choose Scout. If you value leadership, choose Jem. Each of these characters are dynamic, meaning you can approach them in many ways, but those are character traits that are associated with those characters.
Once you have selected your character, the assignment becomes easier. I would write a tribute to your chosen character. If you choose Atticus, write your monologue explaining how and why justice is important in life in general, making sure to throw in a quote or reference to the novel itself. Atticus's famous quote about not knowing someone until you walk a mile in their shoes could be a cool tribute to him. Good luck!